President Ahmadinejad's long-promised Holocaust conference opened in Tehran yesterday to an audience including infamous revisionists, racists and anti-Semites. The only speakers who confirmed the Holocaust as a historical fact were a group of rabbis who criticised its use to justify Israeli abuses against Palestinians.

Mr Ahmadinejad called for the conference last year following Western revulsion at his assertion that the slaughter of six million Jews was a myth. But he missed the event to give a speech at Amir Kabir university, a hotbed of student radicalism, where he was heckled by protesters shouting "death to the dictator" and burning his photograph. In response, he quipped that "it is my honour to burn for the nation's ideals".

The Foreign Minister, Manouchehr Mottaki, opened the Holocaust conference by attacking Western restrictions on "scientific and scholarly study". He said the West did not allow Holocaust denial because it would lead to questions "about the identity of the Zionist regime".

Rabbi Ahron Cohen, from Manchester, a member of Jews Against Zionism, said: "I and many others lost countless friends and relatives who perished by industrial genocide. It is a terrible affront to the memory of those who perished to belittle the guilt of those who committed this crime."

Above the conference hall was an exhibition of books, photographs and DVDs that largely supported the view the Holocaust did not take place or was much exaggerated. Photographs of the Holocaust were labelled "myth", with revisionist explanations labelled "truth". Books by the jailed historian David Irving were prominently displayed.

Mostafa Mohammedi, a Tehran University student who helped set up the exhibition, said: "Between 150,000 and 300,000 Jews died because of the natural causes of war such as famine and air raids. Unfortunately, Iranian schools still teach the official history dictated by the West, but we are campaigning to change that."

David Duke, the former Ku Klux Klan leader, said he was attending the confeence to defend freedom of speech. "We have a Holocaust mafia," said Mr Duke. "It's a shame Iran has to be the nation that calls into question that a world famous historian sits in prison for offering an opinion."

The Australian revisionist Fredrick Töben brought a model of the Treblinka death camp to prove the absence of gas chambers and said he faced arrest on his return.